As a method for wiring formation, methods of applying liquid materials such as an ink-jet method have received attention in recent years. For example, in the case of forming a wiring by an ink-jet method, in general, it is carried out by discharging the material to form a wiring, for example a metal colloidal solution containing metal fine particles in guides (also called as banks) formed along a wiring pattern by an ink-jet apparatus and then baking the material for forming a metal wiring pattern. Such formation of a metal wiring using the ink-jet apparatus is advantageous in terms of the production efficiency and basic properties of the wiring. That is, advantageous points of the formation of a wiring by such an ink-jet method are that the method is effective to save investments with no need of apparatus for sputtering, etching and the like; to reduce waste material is improved, and formation of low resistance wiring by thickening a film of wiring is easier than a film formation method in vacuum atmosphere. The wiring substrate produced in such a manner has been investigated for application to various electronic devices, for example, widely investigated for application to substrates of display apparatus.
As previous methods for forming a wiring except methods of applying liquid materials, sputtering depositing for metal layer, photolithography and etching metal layer process shown in FIG. 12 can be exemplified, however they have no such advantages of the ink-jet methods in terms of the production efficiency and the basic properties of the wiring. Further, in such formation of a wiring, the taper shape is to be controlled depending on the etching conditions and in the case where the film thickness becomes thick, it becomes difficult to control the taper shape and in the case of inverse taper shape, the film to be formed on an upper layer, e.g. a CVD (chemical vapor deposition) film, has a crack.
With respect to a method for forming a wiring by an ink-jet method, a method for patterning surrounded region with guides formed on a substrate then filling with the material to form a wiring by an ink-jet method is disclosed (for example, reference to Patent re-publication WO99/48339 (p. 1 and 2)). In such previous guide and ink-jet methods, as shown in FIG. 13, guides 13 are formed and after that a metal colloidal solution is selectively applied between guides 13 and subjected to thermal treatment to form a wiring 4. However, cracks are formed between the guides 13 made of resin material and the metal wiring 4 and if the guides 13 are removed for preventing cracks, the cross-sectional shape of the wiring tends to be inverse taper shape. That is, the taper shape of the guides 13 is transferred to form the inverse taper shape of the cross-sectional shape of the wiring. Further, generally the thickness of the guides 13 is 1 μm (=10,000 Å) or larger, so that removal is very difficult.
Also, as another method for forming a wiring, a method involving forming lyophobic parts and liquid-repelling parts in prescribed patterns on a substrate surface using an organic molecular film, which has a self-alignment characteristic, selectively applying a liquid in which conductive fine particles are dispersed to the lyophobic parts, and converting the fine particles into a conductive film by thermal treatment to form the conductive film only in the lyophobic parts is disclosed (for example, reference to Japanese Patent Application Laid-Open No. 2002-164635 (p. 1 and 2)). In such previous self-alignment film patterning and ink-jet methods, for example as shown in FIG. 14, after patterning the self-alignment film (monomolecular film) 14, material to form a wiring, e.g. the above-mentioned metal colloidal solution, is selectively applied and subjected to the thermal treatment to form the wiring 4. However, patterning of the self-alignment film (monomolecular film) 14 is difficult, so that the productivity is considerably lowered. Accordingly, in the formation of a wiring using an ink-jet apparatus, there still remains a margin for improvements to improve the productivity and to obtain a component placement substrate with suppressed defects such as cracking by sufficiently utilizing the advantageous points of ink-jet. Such a margin for improvements is common generally in methods for applying liquid materials.